There is presently on the market a hand-held breath alcohol testing device sold by Intoximeters, Inc., 1901 Locust Street, St. Louis, Mo., under the trademark ALCO-SENSOR. The commercial device and its use are described in a 1982 edition of a manual, of record. A different sampling system for a similar device is described in U.S. Pat. No. 3,940,251.
It had been considered by the developers of the fuel cell type testing device that the adsorbtion of alcohol from a breath sample was substantially immediate and complete. This has been found to be mistaken. In a device such as the Alco-Sensor testing device, the fuel cell requires approximately three to five seconds to obtain complete adsorbtion of the alcohol from the breath sample in immediate proximity to the fuel cell.
It has been desirable in such a system to sweep the surface of the fuel cell with the breath sample as slowly as possible. At the same time, it is necessary to take a sample as nearly instantaneously as possible with the reaching of the deep lung breath of the person being tested and before the person stops blowing. Clearly, these two objects are inconsistent.
In the device described hereinafter as prior art, a breath sample inlet was positioned at one side of a fuel cell chamber and a highly restricted diaphragm pump chamber inlet at the other side. Breath from a sample tube was drawn through the breath sample inlet into the fuel cell chamber, across the fuel cell, and into the diaphragm chamber by the release of a spring-biased button that was holding the diaphram down prior to its release and pulls the diaphram away from the fuel cell upon its release. In spite of the restriction of the diaphragm chamber inlet, to obtain the sample within a reasonable time, the flow across the fuel cell occurred within less than one second. This had two results: first, that between ten and twenty percent of the alcohol in the sample was not adsorbed by the fuel cell but passed into the diaphragm chamber where it was effectively isolated from the fuel cell by the highly restricted opening, and, second, when the diaphragm was depressed to reset the device, the alcohol in the breath expelled from the diaphragm chamber started a new fuel cell cycle, requiring an additive time period, on the order of thirty seconds to two minutes, for purging and stabilizing the fuel cell. The effect of the first result was to require adjustment in the calibration of the individual units, and to make the the amount of alcohol adsorbed depend upon the retrieval rate of the button so that anything that influenced the button action, e.g. temperature change, could affect the calibration accuracy. The effect of the second result is to slow the testing process, particularly undesirable when one wants to run a second test as quickly as possible, for example because the person stopped blowing at the critical time or to check a result that seems anomalous.
Various attempts to resolve the problem have been made, including the provision of internal baffles in the fuel cell chamber to form a labyrinth path across the fuel cell, but they have been found ineffective.
It has now been discovered that by eliminating the diaphragm chamber altogether, making the diaphragm in effect one wall of the fuel cell chamber, complete adsorbtion of the alcohol from the breath sample can be attained in about five seconds, and no re-energizing of the fuel cell is produced when the diaphragm is depressed to prepare the sampling system for another breath sample, reducing the cycle time and increasing the accuracy and sensitivity of the device substantially.
One of the objects of this invention is to produce a breath alcohol testing device that is more accurate and recycles more quickly than such devices known heretofore.
Other objects will become apparent to those skilled in the art in the light of the following description and accompanying drawing.